1Kernel driver power_meter
2=========================
3 4This driver talks to ACPI 4.0 power meters.
5 6Supported systems:
7 * Any recent system with ACPI 4.0.
8 Prefix: 'power_meter'
9 Datasheet: http://acpi.info/, section 10.4.
10 11Author: Darrick J. Wong
12 13Description
14-----------
15 16This driver implements sensor reading support for the power meters exposed in
17the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of
18features--a power meter that returns average power use over a configurable
19interval, an optional capping mechanism, and a couple of trip points. The
20sysfs interface conforms with the specification outlined in the "Power" section
21of Documentation/hwmon/sysfs-interface.
22 23Special Features
24----------------
25 26The power[1-*]_is_battery knob indicates if the power supply is a battery.
27Both power[1-*]_average_{min,max} must be set before the trip points will work.
28When both of them are set, an ACPI event will be broadcast on the ACPI netlink
29socket and a poll notification will be sent to the appropriate
30power[1-*]_average sysfs file.
31 32The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
33strings that ACPI provides with the meter. The measures/ directory contains
34symlinks to the devices that this meter measures.
35 36Some computers have the ability to enforce a power cap in hardware. If this is
37the case, the power[1-*]_cap and related sysfs files will appear. When the
38average power consumption exceeds the cap, an ACPI event will be broadcast on
39the netlink event socket and a poll notification will be sent to the
40appropriate power[1-*]_alarm file to indicate that capping has begun, and the
41hardware has taken action to reduce power consumption. Most likely this will
42result in reduced performance.
43 44There are a few other ACPI notifications that can be sent by the firmware. In
45all cases the ACPI event will be broadcast on the ACPI netlink event socket as
46well as sent as a poll notification to a sysfs file. The events are as
47follows:
48 49power[1-*]_cap will be notified if the firmware changes the power cap.
50power[1-*]_interval will be notified if the firmware changes the averaging
51interval.
52